A study by researchers at the Wellcome Trust Centre for Human Genetics at Oxford University has uncovered the key role played by a single gene in how groups of animals diverge to form new species. The study, published today in the journal Nature, restored fertility to the normally-infertile offspring of two subspecies of mice, by replacing part of the Prdm9 gene with the equivalent human version. Despite the nearly 150 million years of evolution separating mice and humans, these ‘humanized’ mice were completely fertile.

New animal species form when groups of animals become isolated and as a result, begin to separate through evolution (a process known as speciation). When these isolated populations meet later, they might be able to breed with each other, but the male offspring are often infertile. Horses and donkeys are an example of such speciation: they can interbreed, but their offspring, mules, are infertile.

‘Our work studied similar infertility in hybrid house mice, whose two parents come from different subspecies found in Western and Eastern Europe’, says Dr Ben Davies from the Nuffield Department of Medicine, the first author on the study. These two sub-species are therefore on the verge of splitting into two entirely different species, since like mules, their offspring are infertile.

Dr Davies and his colleagues studied the Prdm9 gene: this gene is already known to have a role in infertility in mice from different species, and is in fact the only known speciation gene in mammals. However, how speciation might link up to infertility was unknown.

In the past two weeks we’ve learned of a major advance in ongoing efforts to halt the spread of HIV, two separate clinical studies have reported that a daily regimen of a pill called Truvada as a pre-exposure prophylaxis (PrEP) is highly effective in preventing infection in high risk groups. This success is a result…

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Scientists have bred worms with genetically modified nervous systems that can be controlled by bursts of sound waves. The tiny nematodes change direction the moment they are blasted with sonic pulses that are too high-pitched for humans to hear.

The pulses work by switching on motor neuron cells that are genetically modified to carry membrane channels that respond to ultrasonic waves.

Researchers said the worms demonstrate the power of a new procedure, dubbed sonogenetics, in which ultrasound can be used to activate a range of brain, heart and muscle cells from outside the body.

Sreekanth Chalasani, a researcher at the Salk Institute in La Jolla, California, told the Guardian that the procedure could one day replace deep-brain stimulation, an invasive procedure that delivers electrical pulses into people’s brains to treat symptoms of Parkinson’s disease.

Nematode worms do not usually react to ultrasound, but Chalasani found that they did when they were surrounded by a fluid containing microscopic bubbles. The bubbles, he found, amplify the ultrasonic waves which then pass inside the worms. The amplified ultrasound waves act on structures called TRP-4 ion channels, found in the membranes of some of the worms’ cells. The sound waves make these ion channels open up and activate the cells they are attached to, according to a report in Nature Communications.

To make ultrasound-controlled nematodes, Chalasani genetically modified the worms so that some of their motor neurons carried TRP-4 ion channels. When he applied ultrasound to the modified creatures, the sound waves were amplified by the microbubbles and transmitted into the worms, where they switched on the modified motor neurons.

The procedure has some similarities with optogenetics, a groundbreaking tool that allows scientists to switch neurons on and off with pulses of light. But Chalasani said that sonogenetics could have some advantages over that technique. Unlike light, which has to be sent down an optic fibre to the desired location inside the brain, low frequency ultrasound waves can pass through tissue unhindered, and so can be sent into the brain from on top of the skull.

“We believe that, using gene therapy and a therapeutic virus, it may be possible to make target human neurons temporarily susceptible to the ultrasound signal in a clinical setting for certain neurological treatments,” said Chalasani. Other applications could focus on muscle cells and insulin-producing cells, he added.

A team including the scientist who first harnessed the revolutionary CRISPR-Cas9 system for mammalian genome editing has now identified a different CRISPR system with the potential for even simpler and more precise genome engineering.